This invention relates to a rotary hearth furnace of the type having a heating chamber and having a rotatable hearth in the chamber. At a loading position, workpieces are placed in angularly spaced stations on the hearth and are advanced around a circular path in the chamber. During the rotation, the workpieces are heated by heating means disposed within the chamber. After being heated, the workpieces are removed from the hearth at an unloading position which is spaced angularly from the loading position. Once the hearth has been filled or substantially filled with workpieces, a heated workpiece is removed from the hearth at the unloading position each time a cold workpiece is placed on the hearth at the loading position.
In most conventional rotary hearth furnaces, the hearth is intermittently indexed through equal steps each having an angular length equal to the angular spacing between adjacent workpiece stations so that successive workpieces are loaded into adjacent stations when the hearth successively dwells. In addition, the unloading position is usually located closely adjacent the loading position so that each workpiece may be removed from the hearth after the hearth has rotated approximately through a complete revolution.
The loading arrangement used in conventional rotary hearth furnaces results in several cold workpieces being grouped together in the initial zone of the furnace chamber while several extremely hot workpieces are grouped together in the final zone of the chamber. Difficulty has been encountered, therefore, in maintaining temperature uniformity around the chamber since the group of cold workpieces absorbs significantly more heat than the angularly spaced group of extremely hot workpieces. Also, the close proximity of the loadng and unloading positions of a conventional rotary hearth furnace requires a considerable amount of floor space adjacent one section of the furnace and makes it difficult to employ automated equipment for loading and unloading the hearth.